Final Mummy Berry Forecast for Highbush Blueberries

As reported in the 20 May forecast the primary infection period for mummy berry disease is now over in Kings County and lasted from April 23^rd to May 21^st. The list below details the high risk infection periods during this time and overall it has been a pretty good season with only six infection periods documented by the weather station at Tim Strong’s orchard on Brooklyn Street in Kings County; however, growers should expect blight symptoms in the coming days if they have a history of the disease and did not protect at appropriate times.

Note that for the first infection period on April 23^rd/24^th, there was very little inoculum present at that time and only a low percentage of buds of the earliest varieties were susceptible. As such, if orchards were not protected for this infection period they should still expect to see very little damage.

There is a second cluster of three infection periods from May 2 to May 6 that is more problematic as they were in the heart of the season and if orchards were not protected significant losses would be highly likely, particularly if they have a history of the disease. The good news is that these three high risk infection periods are close together and could have all been protected against with a single spray.

The last two infection periods on May 14 and May 19/20 are also close enough that they could have been protected against by a single spray so in fact two well timed sprays would have been sufficient to protect blueberry orchards from primary mummy berry blight infection in 2016, not too bad at all! How may sprays did you make and were they appropriately timed for the infection periods noted below?

The infection periods indicated in the weather data collected at Tim Strong’s on Brooklyn St. Kings County in 2016 were as follows:

1.  12:00 p.m. April 23 to 3:15 a.m. April 24 (15.25 hr wet period, average Temp. 9.1 ⁰C)

2.   20:00 p.m. May 2 to 8:15 a.m. May 3 (12.25 hrs wet period, average Temp. 7.0 ⁰C)

3.   00:30 a.m. May 5 to 13:30 p.m. May 5 (13 hrs wet period, average Temp. 6.6 ⁰C)

4.   20:00 p.m. May 5 to 8:15 a.m. May 6 (12.25 hrs wet period, average Temp. 6.7 ⁰C)

5.   3:15 a.m. May 14 to 13:00 p.m. May 14 (9.75 hrs wet period, average Temp. 11.5 ⁰C)

6.   22:45 p.m. May 19 to 8:15 a.m. May 20 (9.5 hrs wet period, average Temp. 11.0 ⁰C)

How do you know if you have been successful in protecting your plants from infection? If primary infection does occur in your blueberries, blight symptoms will develop 10-20 days from the time of infection. This could be any time now so monitor your orchard regularly over the next week or so for symptoms. These symptoms appear as water soaked or dark brown areas along the midrib and veins of leaves which will soon wilt (Fig.1). Infected blossom clusters become dark purple-brown in color, and shrivel. A characteristic whitish-grey growth of spores (conidia) is produced on the midrib of infected leaves and is very diagnostic for the initiation of the secondary phase of the disease which ultimately results in the actual mummy berries and yield loss.

Remember that this forecast is based on data collected from Tim Strong’s orchard on Brooklyn Street in Kings County and may not be applicable to your location. It is a guide only.  

Figure 1.  Typical leaf blight and wilt symptoms of mummy berry blight in highbush blueberries

Mummy berry blight season winding down!

Apothecia cup samples were collected this morning in Kings County and only a few were still actively sporulatingsuggesting that the primary infection season for mummy berry disease is rapidly winding down in this area. With the warm, dry conditions forecast for today and Saturday it will likely be over completely this weekend and growers in the Annapolis Valley and southwest Nova can breathe easier with respect to this disease. If you are located to the east of the Annapolis Valley the season is progressively later, by as much as 1-2 weeks, and growers in these areas may wish to extend their protection sprays an appropriate period of time.

A final forecast will be prepared next week to review the number and severity of infection periods (as determined by the weather station at Tim Strong’s in Kings County).

Remember that this forecast is based on data collected from Tim Strong’s orchard on Brooklyn Street in Kings County and may not be applicable to your location. It is a guide only.  

Latest Mummy Berry Blight Alert

Two wet periods in the last 36 hrs have both been suitable for mummy berry blight infection!The details of these wet periods at the weather station in Kings County are as follows:

First event:         00:30 hrs May 5^th to 13:30 hrs May 5^th (13 hrs)

Second event:   19:45 hrs May 5^th to 08:00 hrs May 6^th and still running (>12.25 hrs)

 
If you have applied a suitable fungicide within the past 7-10 days you are likely protected. If not, you have within 72 hrs of the beginning of the wet period to apply a control with back-action capability to control any infections during these wet periods. This would mean that you have till 00:30 hrs Sunday May 8^thto apply one of these controls.
 

Registered fungicides with back-action control of mummy berry blight infections include Topas, Mission, and Funginex, although the latter cannot be applied if berries are to be exported to the US. Other newly registered fungicides such as Quash and Indar may have back-action control but have not been tested for this activity so it would be advisable to use Topas, Mission, or Funginex (if you are not exporting).  Refer to Perennia’s Highbush Blueberry Management Schedule at  http://www.perennia.ca/Pest%20Management%20Guides/Fruits/2016/Highbush_I&DGuide_2016.pdffor product formulations and read product labels carefully for product rates and application details.

 
Finally, remember that this forecast is based on data collected from Tim Strong’s orchard on Brooklyn Street in Kings County and may not be applicable to your location. It is a guide only. 

Mummy Berry Infection Alert!

This update is to report that there was a precipitation event on Monday evening and night that was a high risk for mummy berry infection!  If you had a spray on within a week to 10 days before this event you were likely protected.  If you did not, you can still protect your fields from the infection by application of a fungicide with back-action capability within 72 hours of the beginning of the event.  The beginning of the wetting period at the site on Brooklyn Street here in Kings County was recorded at 8 p.m. so growers in this area of Kings County would have until 8 p.m. on Thursday May 5^thto apply a control for back-action protection.

The weather forecast for Kings County is calling for 20-30 mm of rainfall Wednesday night and Thursday so a spray for back action control should be made today while an application window is available.  This spray will protect against the infection period Monday night as well as the one forecast for tonight and tomorrow.

Mummy Berry Forecast - April 29, 2016

Once again, primary infection for mummy berry disease in highbush blueberry requires three conditions to be met:

1. Inoculum presence - mature sporulating apothecia cups,
2. Susceptible bud development stage – bud scales separating in flower buds (F2 stage), and
3. Suitable weather conditions – long wet periods at relatively warm temperatures.

Also, it is not recommended to spray until 40-50% of buds of a given variety are at the F2 stage and there is no need to spray if you have no history of mummy berry disease on your farm.

Observations as of Thursday April 28^st:

• Mature apothecia cups are now present and actively sporulating so we have inoculum present at this time.

• The early variety ‘Bluetta’ had 70% of flower buds at the F2 development stage while the mid-season variety ‘Bluecrop’ was found to have 50% of its flower buds at the F2 stage. The late mid-season variety ‘Nelson’ was at 10% F2 while the late varieties ‘Jersey’ and ‘Burlington’ were at 0% F2. Surprisingly, the early variety ‘Duke’ was only found to be at 10% F2 but it appears most early and mid-season varieties are now at the ideal development stage for infection.

• A 15.5 hr long wet period from Saturday afternoon April 23^rd through to early Sunday morning April 24^th would have been sufficient for a high risk infection period but most (if not all) varieties would not have been at a susceptible bud stage and very little (if any) active spores were present at that time in Kings County; however, we can now say that we are now in the primary ‘mummy berry infection season’ and must either use a “fixed sprayed schedule” to protect bushes from infection or a ‘weather based spray program’ to control infections using controls that have “back-action” capability (eg. Topas).

Recommendations:

A ‘fixed spray schedule’ may be used to manage the disease whereby the first fungicide spray should be applied when 40-50% of the flower buds have reached the F2 stage (flower bud scales separating). One or more additional sprays may be required on a 7-10 day schedule. As such, most early and mid-season varieties would benefit from their first cover as soon as possiblewhile sprays to later season varieties may be delayed until their bud-development reaches the recommended 40-50% F2 stage.

 

Alternatively, a ‘weather based spray schedule’ may be employed. This strategy uses temperature and leaf wetness duration to determine if an infection period has occurred. If an infection period occurs and mature apothecia are present, and flower buds have reached the 40-50% F2, then the grower has up to 72 hours after the start of the wet period to apply Funginex, Mission, or Topas. An additional spray(s) may be required, depending on weather conditions, 7-10 days later. Identification of infection periods for back-action control will be communicated through this forecast in the coming weeks so please stay tuned and have your sprayers ready.

 Finally, please remember that the observations and recommendations above are derived from data collected in Kings County, Nova Scotia and may not be applicable to your location. Once again, if you are to the south and/or west of Tim’s location in Kings County you may well be ahead in development and if you are located to the east of the Valley you will generally be later. This forecast is to be used a guide only for mummy berry disease management in Nova Scotia.

 

Latest Mummy Berry Forecast

A quick reminder that primary infection of mummy berry disease in highbush blueberry requires three conditions to be met:

1. Inoculum presence – mature sporulating apothecia cups,
2. Susceptible bud development stage – bud scales separating in flower buds (F2 stage), and
3. Suitable weather conditions – long wet periods at relatively warm temperatures.

Also, it is not recommended to spray until 40-50% of buds of a given variety are at F2 stage and there is no need to spray if you have no history of mummy berry disease on your farm. For more information and pictures refer to “Management of Mummy Berry in Highbush Blueberry”.

                                                 Flower buds at F2 (bud scales separating)

Observations on Thursday April 21^st:

• Apothecia cups at the “pinhead” stage of development were found but were not actively sporulating and as such there is no inoculum at this time.
• Flower buds are not yet at the 40-50% F2 development stage recommended for spray application.The early variety ‘Bluetta’ had 15% of flower buds at the F2 development stage while Duke, Bluecrop, Nelson, Jersey, and Burlington had 0-4% flower buds at the F2 development stage.
• Showers and light rain is forecast for Saturday April 23^rdand Tuesday April 26^th.

Recommendations:

It is still too early to spray as of April 22^nd (at Tim’s farm), but we are getting close! There are immature apothecia cups present and buds of some early varieties are approaching the 40-50% F2 stage recommended for first spray. Suitable weather conditions for infection (long wet periods and mild temperatures) are possible within the coming week but most varieties will not be advanced enough to warrant protection. 

Note that several fungicides registered for mummy berry disease (eg. Topas) have what is referred to as “back-action” activity and can effectively control an infection if applied within 72 hours of the beginning of the infection period. For a complete list of registered products please refer to “Highbush Blueberry Insect and DiseaseManagement Schedule”.

Finally, please remember that the observations and recommendations above are derived from data collected in Kings County, Nova Scotia and may not be applicable to your location. Once again, if you are to the south and/or west of Tim’s location in Kings County you may well be ahead in development and if you are located to the east of the Valley you will generally be later. This forecast is to be used a guide only for mummy berry disease management in Nova Scotia. 

First Mummy Berry Forecast of 2016

Perennia will be delivering a mummy berry disease forecast for highbush blueberries again in 2016. Please keep in mind that Tim Strong is our co-operator on this project and recommendations will be based on weather data collected on his farm on Brooklyn Street, Kings County, Nova Scotia. It should be fairly accurate for other growers in Kings County but will be a guide only for growers west, south, and east of his location. Westerly and southerly locations are generally a little ahead of the Valley while more easterly locations become progressively later.

To review the disease, its symptoms, and life cycle, please examine the fact sheet on Perennia’s website titled “Management of Mummy Berry Disease in Highbush Blueberry”:

http://www.perennia.ca/Fact%20Sheets/Horticulture/Fruit/Highbush%20Blueberry/Management%20of%20Mummy%20Berry%20Disease%20in%20Highbush%20Blueberry.pdf 

The important thing to remember about the disease is that you need three things for infection to occur – inoculum, susceptible bud development stage, and suitable weather conditions. As of yet, we do nothave buds at the susceptible development stage and no apothecia cups (for inoculum) have been found. However, buds are expanding on early varieties and if mild conditions persist we could well be at susceptible development stages for some varieties over the next week. As such growers should have their sprayers ready to go.

For a review of the fungicides registered for use on this disease please take a look at Perennia’s Highbush Blueberry Insect and Disease Management Schedule found at http://www.perennia.ca/Pest%20Management%20Guides/Fruits/2016/Highbush_I&DGuide_2016.pdf